What are ISO camera settings and what does ISO mean?
ISO stands for International Organisation for Standardisation (it really does - ISO in the dictionary
) and it refers to the industry norm for sensitivity of emulsion based film, with 100 ISO being not so sensitive (and the standard ISO used by most people) to 1600 ISO which is extremely sensitive to light. Click here for the gory details if you really feel the need.
In the beginning for me anyway, I tended to use just 100 as I didn't really know any better. I used 100 ISO for normal, everyday use and kept the 400 for either indoors, black and white
or colour "grainy" shots. 400 ISO was useful for indoor shots where flash couldn't be used, such as some shows, as with the extra sensitivity, I could still get some decent shots.
The major headache with film photography was that if you wanted to change the ISO settings, you had to change the film itself! Not good if you were in a hurry. The beauty of digital, and I have found myself changing ISO settings so much more often now, is that you can alter the ISO for each individual shot. This means, should you come across a situation where you are in low light and cannot use flash, you can just up the ISO settings to 800, 1600 or even 3200 making the sensor a lot more sensitive to light, and fire away knowing the images will come out ok.
If you get in a situation where you have the aperture fully open (i.e. the f/stop number is at its lowest) and the shutter speed selected is too slow to hand hold such as 30th or 15th/sec, use the higher ISO settings, they are like a Godsend in digital photography, especially if you don't carry a flashgun. This is often used by Sports Photographers who will shoot at ISO 400/800/1600 regularly to get the faster shutter speeds a higher ISO offers. Allowing them to more effectively freeze action
The opposite is true here as well. Where high ISO's give grainier, lesser quality images, a low ISO such as 100 or 50 will produce the finest quality, grain free images that your camera is capable of.
With film, anything above ISO 400 would produce grainy and textured images and the techniques in the 80's and 90's for reducing grain were few and far between. However, with the new breed of digital cameras the "noise" as it is also known, is barely noticeable in some images and some camera's now go as high as ISO 25,600
Even if a bit of grain or noise does appear, there are programs such as Neat image available that will all but remove any signs of grain/noise...amazing!
If you own a digital SLR, play with these ISO settings to see how it can improve your photography. Purposely leave your flash at home and turn the ISO settings right up to see how it functions. Heavy grain in some images such as buildings or landscapes can really add great, moody effects to your shots. Grain/Noise in black and white photography can look exceptionally pleasing.
Refer to this f/stop chart
for a shutter speed vs f/stop table and explanation of how shutter speed, aperture and ISO sensitivity relate together in what is referred to as the exposure triangle.